Thanks everyone for the additional information & yes Ron your correct with not knowing if I am above or below the desired setting, the idea with the coloured LEDs is a good one & obviously something I never thought of.
I have been simulating some circuits on Ltspice & realised myself that the window is far to tight considering the manual adjustments that are required to get the correct "Vacuum Pressure" from my machine.
KeepitSimpleStupid, I hope it's ok if I refer to you as T to save me writing your user name all the time & because of other reasons.
Yes your correct, a pressure controller is what is required but they are expensive.
I have been manually adjusting the Vacuum Pressure for many years & it is time for a change.
If you could point me in the right direction I would like to have a go at building a controller, can this be done with Hardware only such as a PI or PID controller?
My machine operates from 240AC so I guess there are two ways of controlling it, firstly by altering the speed of the Motors or by using a Servo Valve to restrict a conduit to obtain the correct pressure?
Any advise would be greatly appreciated.
Cheers